The present invention relates generally to the field of thermal management structures for power electronic circuits and the like. More particularly, the invention relates to the cooling of resistors, such as brake resistors used in inverters and other power electronic devices.
Resistors are used in power electronic devices for a range of reasons. Firstly, such resistors may operatively figure as part of the overall power signal conditioning or control scheme. However, other resistors are used to dissipate energy, such as in the case of motor drives, power converters, and so forth. Such brake resistors may be associated, for example, with a DC bus extending between a rectifier and a converter (e.g., an inverter). The resistors may be switched into the circuit when necessary to dissipate energy, such as for braking an inertial load. Because resistors develop significant heat due to their internal resistance and the current flowing through them during operation, heat dissipation is often a challenge for their use.
Conventional approaches to cooling resistors, particularly brake resistors, having included the use of monolithic heat spreaders, radiant and convective thermal transfer, and transfer to a circulated cooling medium, such as water. However, in many settings, the resistors may generate more heat than can be adequately transmitted to the environment by conventional means. Water circulating systems are often undesirable due to their complexity and the potential for leaks. Many conventional cooling schemes also fail adequately to reduce temperature differences or gradients in structures surrounding the resistor.
There is a need, therefore, for improved approaches to thermal management of resistive structures, such as brake resistors. There is particular need for a technique which would allow for heat to be extracted from a brake resistor in a packaged or modular structure, and that would render the structure and the overall circuitry more isothermal than conventional arrangements.